Researchers have detected a flaw in the popular USB devices that everyone loves. Not just on certain devices, practically every single USB device can be exploited, which puts the number of in the billions. What made the USB so widely accepted in the first place is actually the fundamental reason why it can be manipulated. Basically, the host machine (in most cases computers) identifies the USB device according to its class and controls it using class drivers, and it is in this process that the flaw comes into play
Every USB device has a controller which, as its name implies, controls the connection to other devices through firmware that can be reprogrammed. As you may have realized it can be reprogrammed to act maliciously, and the worst part is that detecting the reprogramming of the firmware is virtually impossible to detect.
By reprogramming the controller the USB device can change its class and, for example, a flash drive can act like a keyboard. This would the flash drive to issue keyboard commands that could install malware and/or rewrite the firmware of other USB devices that are attached to the host machine.
Security issues with the USB may not be new but this type of attack is different because there is no known effective defense against it. It is virtually impossible to spot the change in the firmware unless you know exactly where to look, and the average computer user will not know this information. Malware scanners, by design, can’t access the firmware of USB devices so that solution is out the window. It is possible that in the future some defenses may become available, but currently the only precaution you can take is to only use devices that you trust 100%. On August 7, 2014 at Black Hat 2014, Security Research Labs is expected to release more details and potential tools to mitigate this security flaw.